Detection of liposomes in portal blood following oral administration

125Iodine-labeled human immunoglobulin G-encapsulated dipalmitoyl phosphatidylcholine liposomes were prepared with or without asialoganglioside. Distribution of radioactivity following the oral administration of these liposomes in rats was checked in liver and in blood of the portal vein and heart. Gel filtration of plasma from the portal vein showed the presence of intact liposomes and protein. In contrast, neither liposomes nor protein were detected in cardiac blood but only lower molecular weight materials. The presence of liposomes in portal blood was further suggested from experiments using 6-carboxyfluorescein-entrapped liposomes. The level of liposomes in portal venous blood plasma was found to be lower in asialoganglioside liposomes. But this level could be increased substantially, almost to that in liposomes without asialoganglioside, by injection (iv) of asialofetuin.